org.jfree.data.general.SeriesException: You are attempting to add an observation for the time period Wed Dec 31 18:00:11 CST 1969 but the series already contains an observation for that time period. Duplicates are not permitted. Try using the addOrUpdate() method.

org.jfree.data.general.SeriesException: You are attempting to add an observation for the time period Wed Jun 08 12:34:56 WEST 2016 but the series already contains an observation for that time period. Duplicates are not permitted. Try using the addOrUpdate() method.

org.jfree.data.general.SeriesException: You are attempting to add an
observation for the time period Mon Jun 06 10:35:52 BRT 2016 but the series
already contains an observation for that time period. Duplicates are not
permitted. Try using the addOrUpdate() method.